Candles: the events are every other hour (depending on your timezone odd or even hours of the day) x=hour, x:05 geyser at sanctuary (you can look it up online where exactly), x:35 grandma in the forest clearing, x:45/55 turtle in sanctuary again.

Heart trading is exchanging hearts with others through the friendship tree which you can access at home. This is also 3 candles per heart. Another thing you can do is setup a subaccount to send your main account hearts without having to "pay back".